# -*- coding: UTF-8 -*-
'''
Created on 2012-6-21


对象与参考
如果你想要复制一个列表或者类似的序列或者其他复杂的对象（不是如整数那样的简单 对象 ），
那么你必须使用切片操作符来取得拷贝。如果你只是想要使用另一个变量名，
两个名称都 参考 同一个对象，那么如果你不小心的话，可能会引来各种麻烦
@author: Administrator
'''
print 'Simple Assignment'
shoplist = ['apple', 'mango', 'carrot', 'banana']
mylist = shoplist # mylist is just another name pointing to the same object!

print id(shoplist)
print id(mylist)

del shoplist[0]

print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that both shoplist and mylist both print the same list without
# the 'apple' confirming that they point to the same object

print 'Copy by making a full slice'
mylist = shoplist[:] # make a copy by doing a full slice
print id(shoplist)
print id(mylist)
del mylist[0] # remove first item

print 'shoplist is', shoplist
print 'mylist is', mylist
# notice that now the two lists are different
